Technically, they released Opus 4.1 a few weeks ago, so that alone hints at a smaller leap from 4.1 -> 4.5, compared to the leap from Sonnet 4 -> 4.5. That is, of course, if those version numbers represent anything but marketing, which I don't know.
I had forgotten that, given that Sonnet pretty much blows Opus out of the water these days.
Yeah, given how multi-dimensional this stuff is, I assume it's supposed to indicate broad things, closer to marketing than anything objective. Still quite useful.